Revised standard weight equation and length categories for Spotted Bass and new proposed standard weight equation and length categories for Alabama Bass

ABSTRACT Objective Spotted Bass Micropterus punctulatus and Alabama Bass M. henshalli have been recognized as separate species for close to two decades, yet they continue to be managed as a single species under the same standard weight (Ws) equation and length categories despite known differences in body form and growth potential. The objective of this study was to develop and assess new Ws equations and length categories for proportional size distribution indices to better inform management decisions for each species. Methods Length and weight data for Alabama Bass were obtained from 32 populations across six states, totaling 41,341 individuals; data for Spotted Bass were obtained from 127 populations across 11 states, totaling 86,602 individuals. Using these data, three new Ws equations were created for both species with the regression line percentile, empirical percentile–linear (EmP-L), and empirical percentile–quadratic techniques. New standard length categories were derived from the current International Game Fish Association world record for Alabama Bass and from the mean of state records from 10 states for Spotted Bass. Results For Alabama Bass, all three techniques produced reasonable Ws equations that dramatically outperformed the old equation. For both species, the EmP-L and empirical percentile–quadratic equations displayed less length bias in relative weight estimates than the regression line percentile equation, but neither empirical percentile equation was notably superior. Therefore, we propose that the new Ws equations for both species should be the simpler EmP-L version following the suggestions of previous studies. With total length (TL) in millimeters and weight (WT) in grams, the Alabama Bass equation is log10(WT) = −5.6189 + 3.284·log10(TL) and the Spotted Bass equation is log10(WT) = −5.3467 + 3.197·log10(TL). The old standard length categories proposed for Spotted Bass should be retained for Alabama Bass; those values are 180, 280, 350, 430, and 510 mm TL, representing stock, quality, preferred, memorable, and trophy categories, respectively. For Spotted Bass, we propose the following standard length categories: 150, 230, 300, 350, and 440 mm TL, respectively. Conclusions These Ws equations and standard length categories better match the body form and growth potential of both species and will provide biologists with improved tools to monitor the condition and size structure of these important sport fishes.